Fertilizer compositions carrying an aminoalkanol as anticake agent

ABSTRACT

The tendency of particles of water-soluble hygroscopic salts and fertilizers containing water-soluble hygroscopic salts to cake when allowed to stand is decreased when the particles have a uniformly distributed surface content of an aminoalkanol material selected from the group consisting of (1) a mixture of vicinal aminoalkanols of the formula: ##STR1## wherein R 1  and R 2  each represent H or --(CH 2 ) 1-18  H; R 1  and R 2  together contain 9-18 carbon atoms; and R 3  and R 4  each represent H, C 1-4  alkyl and C 2-4  hydroxyalkyl; and (2) salts thereof with water-soluble acids. 
     The aminoalkanols can be applied from organic solvent or water solution, or as a hot melt.

FIELD OF INVENTION

The present invention relates to solid hygroscopic salts (and mixtures of hygroscopic salts including synthetic fertilizers) in particulate, free-flowing state of reduced tendency to cake on storage. The invention includes the modified particles themselves and methods for treating the particles to decrease their tendency to cake.

BACKGROUND OF INVENTION

As known, many inorganic salts and oxides, among them components of mixed fertilizers like potassium chloride and the nitrogenous salts (ammonium nitrate, ammonium sulfate, sodium nitrate and diammonium phosphate) are hygroscopic and therefore cake or coalesce when stored, particularly at elevated humidity, temperature and pressure. Materials of this type are not suitable for storage in bulk since after such storage they cannot be spread readily by mechanical spreaders.

In order to reduce caking, hygroscopic materials of this type (including fertilizers) are produced in the form of pellets or "prills" of equal size which are coated with talcum, kieselguhr, diatomaceous earth or chalk in order to prevent absorption of moisture. But in these methods large amounts of one or more of these anti-caking agents must be added, so that when the material is a fertilizer its nutrient content is reduced and in any event considerable dust is developed when the coated particles are spread.

U.S. Pat. No. 2,480,694 discloses that fatty amines and their derivatives prevent the caking of fertilizers. Solutions of fatty amines in mineral oil and the spraying of these solutions on fertilizers are described in U.S. Pat. No. 3,186,828. In general, fatty amines (including fatty diamines) which contain a fatty radical of 8 to 22 carbon atoms, as well as their salts (particularly the acetates and chlorides) and their ethoxylates, are used. But these methods and products have the disadvantage that the anticaking effect achieved with fatty amines and their derivatives is not satisfactory. It is difficult to apply the solid fatty amines evenly to the salt or fertilizer material; and the products are not harmless because of their strong amine odor and their tendency to irritate the eyes and skin.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a hygroscopic salt material (including synthetic fertilizers) in free-flowing, particulate form with a surface content of a material which will inhibit the tendency of said particles to cake on storage.

It is a further object of the invention to provide such a composition wherein the anti-caking component is effective when present in very minor amount.

It is a further object of the invention to provide such a composition wherein the anti-caking composition has no perceptible effect upon the ecology, is substantially odorless, and is comparatively harmless from the dermatological point of view.

Finally, it is an object of the invention to produce non-caking, water-soluble particles of said salt material without need for organic solvents and preferably without need for water as solvent.

THE INVENTION

It has now been found that the tendency of salts and chemical fertilizers to cake on standing is decreased to a surprisingly great extent when the anti-caking agent is

(1) a mixture of vicinal aminoalkanols of the formula: ##STR2## wherein R₁ and R₂ each denote hydrogen and/or unbranched alkyl radicals with 1 to 18 carbon atoms, where the sum of the carbon atoms in R₁ and R₂ is 9 to 18, where the radicals R₃ and R₄ can be the same or different and denote hydrogen, alkyl radicals with 1 to 4 carbon atoms or hydroxyalkyl radicals with 2 to 4 carbon atoms, where x represents a value of 2 to 6 and y represents a value of 0 to 1, the ##STR3## units in the aminoalkanols of said mixture being of at least two different chain lengths in the range from 11 to 20 carbon atoms; and (2) salts of the aminoalkanols in said mixture.

As starting materials for the production of the mixtures of aminoalkanols according to the invention, a variety of olefin mixtures can be used.

Suitable mixtures of monoolefins are obtained by dehydrogenation (catalytically or by chlorination followed by dehydrochlorination) of linear paraffins of 8 to 24 carbon atoms followed by removal of the monoolefin content of the reaction product (by distillation or selective extraction as may be preferred). In these monoolefins the double bonds are substantially non-terminal and are distributed statistically (i.e., randomly) along the "backbone" ##STR4## chain.

With regard to chain length, preferred monoolefins conform to the chain length distribution shown in the examples below.

On the other hand, it is also possible to use olefin mixtures which are prepared by aluminochemical methods and which have unbranched alkyl chains with 12 to 20 carbon atoms. These mixtures have a high proportion of terminal unsaturation, and commercial products are suitable which have length distributions shown in the examples.

The position of the vicinal ##STR5## units on the ##STR6## chain is therefore not critical. It is preferred, however, that units be terminally located, one of R₁ or R₂ is hydrogen.

The monoolefin mixtures are converted by known methods, for example, by reaction with per acids like peracetic acid, to the corresponding epoxide mixtures, from which aminoalkanol mixtures suitable for use according to the invention are obtained by reaction with amines like ammonia, methylamine, ethylamine, butylamine, dimethylamine, diethylamine, methylethylamine, ethylenediamine, propylenediamine, monoethanolamine, diethanolamine and N-ethanol-ethylene-diamine.

The salts of the aminoalkanol mixtures with inorganic acids and aliphatic carboxylic acids with 2 to 20 carbon atoms, particularly with water-soluble acids like hydrogen chloride and acetic acid, can be prepared according to conventional methods.

Salts and salt-containing fertilizer compositions exhibit resistance to caking on storage when having a surface content of the aforementioned aminoalkanols, and in preferred embodiments they are far superior to such compositions carrying a fatty amine or fatty amine derivative of a fatty acid or alcohol.

Preferred anti-caking agents are aminoalkanol mixtures which are derived from monoolefin mixtures with substantially terminally located double bonds and chain lengths of 12 to 20 carbon atoms.

Preferably therefore, in the formula given above, the ##STR7## group occupies a terminal position on the ##STR8## chain.

Due to their relatively low flow points, most of the aminoalkanols described herein can be easily applied by spray while the particulate component is tumbled in a suitable mixing apparatus, for example, in a rotary drum mixer or screw conveyer mixture, directly on the salt or fertilizer composition and can thus be distributed evenly on the particles. Thus there is no need to apply them as a solution (for example, in mineral oil). The products with higher solidifying points can be applied either as a solution in an organic solvent, e.g. mineral oil, or they can be applied directly to the material as a solvent-free melt at a temperature above their flow point (e.g., 60° to 80° C.). When applied in this manner the aminoalkanols are contained only on the surface of the particles. The aminoalkanol mixtures can be applied as free bases or as salts with water-soluble acids or with water-insoluble acids, at least up to the C₂₀ acids. They can also be applied as solutions in solvents or water.

The amount of anti-caking agent according to the invention that is necessary to significantly decrease the caking properties of salts and fertilizers is very small. It ranges from 0.05 to 0.2% of the weight of the salt component to which it is applied.

A suitable amount of the anti-caking agent can be determined in any instance by making a series of trials with increasing amounts of agent within the range mentioned.

When the aminoalkanol is applied as a solution or dispersion, the content of the agent, particularly if the products are used as salts, is preferably between 25% and 100% of the weight of the dispersion medium or solvent used.

Another advantage of the invention is that the aminoalkanol mixtures are considerably safer to handle since they have only weak amine odor and are less dangerous to eyes and skin than corresponding fatty amines.

The use of the products according to the invention as anti-caking agents is described more fully below on the basis of examples. These examples are merely illustrative, and are not to be construed in limitation of the invention.

EXAMPLES

The aminoalkanol mixtures, which are prepared by reacting the olefin-epoxide mixtures and amines and which were tested for use an anti-caking agents, are listed in Table 1 below. The following tabulation identifies the epoxide mixtures, the chain lengths, position of the olefinic double bonds and composition in terms of chain length distribution of the olefins from which the aminoalkanols disclosed below were prepared. All percentages are approximate percentages by weight.

    ______________________________________                                         Olefin Fractions Used                                                                                 Approx.                                                 Fraction               % by Wt.                                                ______________________________________                                         (a)     C.sub.11 -C.sub.14 Fraction                                            C.sub.11,  Non-terminal        22                                              C.sub.12,  "                   30                                              C.sub.13,  "                   26                                              C.sub.14,  "                   22                                              (b)     C.sub.15 -C.sub.18 Fraction                                            C.sub.15,  Non-terminal        26                                              C.sub.16,  "                   35                                              C.sub.17,  "                   31                                              C.sub.18,  "                    6                                              (c)     C.sub.12 /C.sub.14 Fraction                                            C.sub.12,  Terminal            55                                              C.sub.14,  "                   31                                              C.sub.12,  Non-terminal         5                                              C.sub.14,  "                    8                                              (d)     C.sub.14 /C.sub.16 Fraction                                            C.sub.14,  Terminal            53                                              C.sub.16,  "                   28                                              C.sub.14,  Non-terminal         7                                              C.sub.16,  "                   11                                              (e)      C.sub.16 /C.sub.18 Fraction                                           C.sub.16,  Terminal            35                                              C.sub.18,  "                   23                                              C.sub.20,  "                    2                                              C.sub.16,  Non-terminal        11                                              C.sub.18,  "                   21                                              C.sub.20,  "                    5                                              ______________________________________                                    

                                      TABLE 1                                      __________________________________________________________________________     Aminoalkanol Used                                                                           Starting                                                                  Solid                                                                               Epox.                                                             Desig..sup.1                                                                           Pt. ° C..sup.2                                                               Olefin.sup.3                                                                         Amine Substituent                                           __________________________________________________________________________     N-T58 M -3   C.sub.15 -C.sub.18                                                                  Methylamine                                                                           --NHCH.sub.3                                          T24 M   49   C.sub.12 /C.sub.14                                                                  "      "                                                     T24 E   53   C.sub.12 /C.sub.14                                                                  Ethylamine                                                                            --NH(CH.sub.2 CH.sub.3)                               N-T14 DM                                                                               -66  C.sub.11 -C.sub.14                                                                  Dimethyl-                                                                             --N(CH.sub.2).sub.3                                                     amine                                                        N-T58 DM                                                                               -34  C.sub.15 -C.sub.18                                                                  Dimethyl-                                                                             "                                                                       amine                                                        T24 DM  -25  C.sub.12 /C.sub.14                                                                  Dimethyl-                                                                             "                                                                       amine                                                        T46 DM  -1   C.sub.14 /C.sub.16                                                                  Dimethyl-                                                                             "                                                                       amine                                                        N-T14 A -5   C.sub.11 -C.sub.14                                                                  Ammonia                                                                               --NH.sub.2                                            N-T58 A 16   C.sub.15 -C.sub.18                                                                  "      "                                                     N-T14 AE                                                                               14   C.sub.11 -C.sub.14                                                                  Ethylene-                                                                             --NHCH.sub.2 CH.sub.2 NH.sub.2                                          diamine                                                      N-T58 AE                                                                               18   C.sub.15 -C.sub.18                                                                  Ethylene-                                                                             "                                                                       diamine                                                      T24 AE  47   C.sub.12 /C.sub.14                                                                  Ethylene-                                                                             "                                                                       diamine                                                      T46 AE  65   C.sub.14 /C.sub.16                                                                  Ethylene-                                                                             "                                                                       diamine                                                      T68 AE  66   C.sub.16 /C.sub.18                                                                  Ethylene-                                                                             "                                                                       diamine                                                      N-T14 AP                                                                               -37  C.sub.11 -C.sub.14                                                                  Propylene-                                                                            --NH(CH.sub.2).sub.3 NH.sub.2                                           diamine                                                      N-T58 AP                                                                               -28  C.sub.15 -C.sub.18                                                                  Propylene-                                                                            "                                                                       diamine                                                      T24 AP  50   C.sub.12 /C.sub.14                                                                  Propylene-                                                                            "                                                                       diamine                                                      T46 AP  72   C.sub.14 /C.sub.16                                                                  Propylene-                                                                            "                                                                       diamine                                                      T68 AP  71   C.sub.16 /C.sub.18                                                                  Propylene-                                                                            "                                                                       diamine                                                      N-T14 HE                                                                               -23  C.sub.11 -C.sub.14                                                                  Monoethy-                                                                             --NH(CH.sub.2 CH.sub.2 OH)                                              anolamine                                                    N-T58 HE                                                                               -17  C.sub.15 -C.sub.18                                                                  Monoethy-                                                                             "                                                                       anolamine                                                    N-T14 DHE                                                                              -17  C.sub.11 -C.sub.14                                                                  Diethanol-                                                                            --N(CH.sub.2 CH.sub.2 OH).sub.2                                         amine                                                        N-T58 DHE                                                                              -21  C.sub.15 -C.sub.18                                                                  Diethanol-                                                                            "                                                                       amine                                                        T24 DHE -10  C.sub.12 /C.sub.14                                                                  Diethanol-                                                                            "                                                                       amine                                                        T46 DHE 24   C.sub.14 /C.sub.16                                                                  Diethanol-                                                                            "                                                                       amine                                                        T68 DHE 27   C.sub.16 /C.sub.18                                                                  Diethanol-                                                                            "                                                                       amine                                                        N-T14 HE-AE                                                                            -2   C.sub.11 -C.sub.14                                                                  N-ethanol-                                                                            --NHCH.sub.2 CH.sub.2 NH(CH.sub.2 CH.sub.2 OH)                          ethylene-                                                                      diamine                                                      N-T58 HE-AE                                                                            2    C.sub.15 -C.sub.18                                                                  N-ethanol-                                                                            "                                                                       ethylene-                                                                      diamine                                                      __________________________________________________________________________      .sup.1 (T = terminal)                                                          (N-T = non-terminal)                                                           .sup.2 Solidification point, ° C.                                       .sup.3 Starting epoxidized olefin.                                       

To provide a comparison, the following commercial natural fatty amines and fatty diamines were also employed:

Distilled coconut alkyl amine

Distilled tallow alkyl amine

Distilled N-coconut-alkyl-aminopropylamine [i.e., N-coconut alkyl (trimethylenediamine)]

Tallow alkyl aminopropylamine [i.e., N-tallow alkyl (trimethylenediamine)]

The following hygroscopic, caking salts and fertilizers were used for testing the anti-caking action of the above aminoalkanols:

(a) Potassium chloride

(b) "50% potassium" fertilizer;

composition:

Kcl: 80.58%

K₂ so₄ : 3.00%

naCl: 13.17%

MgSO₄ : 2.25%

(c) N-P-K Fertilizer

active substances:

N: 14%

p₂ o₅ : 12%

k₂ o: 17%

composition:

K₂ so₄ : 32.6%

nh₄ h₂ po₄ : 25.0%

urea: 9.4%

(NH₄)₂ SO₄ : 33.0%

(d) Calcium ammonium nitrate

active substances:

N: 23%

ca: 15%

composition:

Nh₄ no₃ : 65%

caCO₃ : 35%

Testing Method

The salts and fertilizers are dried and screened, and a weighed amount of the 0.8 mm.-1.0 mm. fraction is mixed in a Loedige mixer for five minutes. Then 0.1% of the aminoalkanol to be tested, based on the weight of the salts, is added to the fertilizer and the mixing is continued for five minutes. When the aminoalkanol to be tested is a solid at room temperature, the salt and the aminoalkanol are separately heated for 30 minutes at 70° C. before they are mixed.

Depending on the product to be tested, a small amount (100 g. or 125 g.) of the mixture is placed in a glass test tube (44 mm. in diameter and 100 mm. long, with roughened inner surface), at the bottom of which is placed an anchor disc (15 mm. in diameter). The substance to be tested is compressed for 30 minutes under a polyvinyl chloride plunger weighing 10 kg.

The force required to pull out the anchor disc is measured and is a measure of the anti-caking action of the aminoalkanols. The table contains in each case the mean value of six measurements. The smaller the force required to pull out the anchor disc, the smaller is the tendency of the salt or fertilizer to cake. In the table, the designation T indicates that the vicinal substituents are terminally located, and the designation N-T indicates that the vicinal substituents are located non-terminally.

EXAMPLE 1

The effectiveness of short-chained products with substantially terminal vicinal hydroxy and amino groups as anti-caking agents for potassium chloride, 50% potassium fertilizer ("50%K" fertilizer) and N-K-P fertilizer is shown in Table 2. The force required to remove the anchor disc is shown in grams. Practically all the aminoalkanols tested were more effective than coconut alkyl amine or coconut alkyl aminopropyl amine.

                  TABLE 2                                                          ______________________________________                                                     Grams to Remove Anchor Disc from                                   Anti-caking            50%K       N-P-K                                         Agent        KCl      Fertilizer Fertilizer                                   ______________________________________                                         Untreated     1398     283        575                                          T24 M         306      --         449                                          T24 DM        233      --         --                                           T46 DM        326      --         --                                           T24 E         164      --         465                                          T24 AE        303      174        180                                          T46 AE        303      174        180                                          T24 AP        222      265        184                                          T46 AP        244      197        229                                          T24 DHE       150      186        448                                          T46 DHE       153      211        --                                           Coconut alkyl amine                                                                          524      200        506                                          Coconut alkyl amino-                                                           propylamine   389      224        678                                          ______________________________________                                    

EXAMPLE 2

This example shows the effectiveness of the shortchain products with substantially non-terminal vicinal hydroxy- and amino groups against the caking of N-P-K fertilizer. The aminoalkanol mixtures according to the invention yield better results than "natural" amines, as can be seen from Table 3.

                  TABLE 3                                                          ______________________________________                                                             Grams to Remove                                            Anti-caking         Anchor Disc from                                            Agent              N-P-K Fertilizer                                           ______________________________________                                         Untreated           575                                                        N-T14 A             439                                                        N-T14 DHE           322                                                        N-T14 HE            331                                                        N-T14 HE-AE         285                                                        Coconut alkyl amine 506                                                        Coconut alkyl amino-                                                           propylamine         678                                                        ______________________________________                                    

EXAMPLE 3

The anti-caking action of the longer-chain products with substantially terminal vicinal hydroxy- and amino groups on potassium chloride, 50% potassium fertilizer, and N-P-K fertilizer is shown in Table 4.

                  TABLE 4                                                          ______________________________________                                                     Grams to Remove Anchor Disc from                                   Anti-caking            50%K       N-P-K                                         Agent        KCl      Fertilizer Fertilizer                                   ______________________________________                                         Untreated     1398     283        575                                          T68 AE        265      232        249                                          T68 AP        214      211        211                                          T68 DHE       150      213        329                                          Tallow alkyl amine                                                                           478      233        332                                          Tallow alkyl amino-                                                            propylamine   291      239        325                                          ______________________________________                                    

EXAMPLE 4

In this example we tested the anti-caking effect of the longer-chain aminoalkanol mixtures with substantially terminal hydroxy- and amino groups on the caking of 50% potassium fertilizer and calcium ammonium nitrate, compared to the anti-caking effect of amines based on natural fats. Here too, the products according to the invention show better results than the natural products, as can be seen from Table 5.

                  TABLE 5                                                          ______________________________________                                                     Grams to Remove Anchor Disc from                                   Anti-Caking   50%K        Calcium                                               Agent        Fertilizer  Ammonium Nitrate                                     ______________________________________                                         Untreated     283         1495                                                 N-T58 A       204         1079                                                 N-T58 AE      217         1074                                                 N-T58 AP      252         1177                                                 N-T58 DHE     201         1186                                                 N-T58 HE      218         1182                                                 N-T58 HE-AE   209         1214                                                 Tallow alkyl amine                                                                           233         1246                                                 Tallow alkyl amino-                                                            propylamine   239         1219                                                 ______________________________________                                    

EXAMPLE 5

Other aminoalkanol products according to the invention from Table 1 with substantially non-terminal hydroxy- and amino groups were tested for their effectiveness. It can be seen from the results compiled in Table 6 that the tested products according to the invention, showed a better anti-caking effect than the comparison products.

                  TABLE 6                                                          ______________________________________                                                             Grams to Remove                                                               Anchor Disc from                                            Anti-caking                     N-P-K                                           Agent               KCl        Fertilizer                                     ______________________________________                                         Untreated            1398       575                                            N-T58 M              337        277                                            N-T14 DM             321        437                                            N-T58 DM             309        --                                             Coconut alkyl amine  524        506                                            Coconut alkyl amino-                                                           propyl amine         389        678                                            ______________________________________                                    

EXAMPLE 6

The anti-caking effect of certain of the above-described aminoalkanols in the form of their acetate and chloride salts was also determined. The aminoalkanol salts were applied as aqueous solutions having a content in the range 30% to 70% by weight thereof. The solutions were applied at such rate as to deposit 0.1% of the aminoalkanol based on the weight of the material treated. Table 7 shows that these aminoalkanols provide a better anti-caking effect than the corresponding salts of the natural comparison substances.

                  TABLE 7                                                          ______________________________________                                         Anti-caking Agent Salt                                                                          % in                                                                           Treating  Grams to Remove                                     Name             Solution  Disc from KCl                                       ______________________________________                                         Untreated                  1398                                                N-T58 A (Acetate)                                                                               60        284                                                 N-T58 AE (Diacetate)                                                                            60        251                                                 N-T58 AP (Diacetate)                                                                            --*       356                                                 Tallow alkyl amine (acetate)                                                                    --*       428                                                 N-T14 A (Chloride)                                                                              60        148                                                 N-T14 AE (Dichloride)                                                                           30        428                                                 N-T14 AP (Dichloride)                                                                           40        429                                                 Coconut alkyl amine chloride                                                                    35        498                                                 N-T58 A (Chloride)                                                                              40        174                                                 N-T58 AE (Dichloride)                                                                           40        446                                                 N-T58 AP (Dichloride)                                                                           35        469                                                 Tallow alkyl amine chloride                                                                     35        475                                                 ______________________________________                                          *Substance was not applied in solution but by hot melt method.           

EXAMPLE 7

The dermatological tolerance of the aminoalkanol mixtures was tested by dropping small amounts of 2.5% solutions of the test substances in olive oil into the conjunctival sac of one eye of groups of albino rabbits. The reactions of the mucous membranes of the eye were evaluated according to a point system by Draize [Appraisal of the Safety of Chemicals in Foods, Drugs and Cosmetics, Assn. of Food and Drug Officials of the U.S., pp. 49-52 (1959)], for two hours, 1, 2, 4, 6 and 8 days after the application.

The results of the test are compiled in Table 8.

                  TABLE 8                                                          ______________________________________                                         Anti-caking Aminoalkanol                                                                  Conc. %   Compatibility with                                        Desig.     By Wt.     Mucous Membrane                                          ______________________________________                                         N-T14 A    2.5%      Moderate conjunctival re-                                                      action practically dis-                                                        appeared after 24 hours;                                                       normal after 2 days.                                      N-T58 A    2.5%        "                                                       N-T14 AE   2.5%      Moderate conjunctival re-                                                      action; normal after 4 days.                              N-T58 AE   2.5%        "                                                       N-T14 AP   2.5%      Strong conjunctival reaction;                                                  normal after 6 days.                                      N-T58 AP   2.5%      Moderate conjunctival re-                                                      action practically dis-                                                        appeared after 4 days.                                    N-T14 DHE  2.5%      Slight conjunctival reaction;                                                  normal after 1 day.                                       Dodecylamine                                                                              2.5%      Moderate conjunctival re-                                                      action; normal after 4 days.                              Dodecylamino-                                                                             1.0%      Strong conjunctival reaction.                             propylamine          After 8 days still 30%-40%                                                     of the maximum reaction.                                  ______________________________________                                     

We claim:
 1. A composition in particulate, free-flowing form consisting essentially of a hygroscopic salt component which normally cakes on storage having a uniformly distributed, effective surface content as anti-caking agent of from 0.05% to 0.2% by weight of said hygroscopic salt component of an aminoalkanol material selected from the group consisting of(1) a mixture of fatty vicinal aminoalkanols of the formula: ##STR9## wherein R₁ and R₂ each represent a substituent selected from the group consisting of H and unbranched alkyl having from 1 to 18 carbon atoms, and the sum of the carbon atoms in R₁ and R₂ is from 9 to 18; R₃ and R₄ each represent a substituent selected from the group consisting of H, C₁₋₄ alkyl and C₂₋₄ hydroxyalkyl; and x represents a value from 2 to 6 and y represents a value from 0 to 1, inclusive, the ##STR10## units in the aminoalkanols of said mixture being of at least two different chain lengths in the range from 11 to 20 carbon atoms; and (2) salts of said aminoalkanols.
 2. A composition according to claim 1 wherein R₁ and R₂ each represent a C₁ -C₁₈ straight chain alkyl substituent.
 3. A composition according to claim 1 wherein R₂ represents H.
 4. A composition according to claim 1 wherein R₃ and R₄ each represent C₁₋₄ alkyl.
 5. A composition according to claim 1 wherein said hygroscopic salt component is a mixture of fertilizer salts.
 6. A composition according to claim 1 wherein the ##STR11## units are of C₁₆ -C₁₈ chain length.
 7. A composition according to claim 1 wherein said hygroscopic salt component is a water-soluble, inorganic salt fertilizer.
 8. A composition according to claim 1 wherein said hygroscopic salt component is calcium ammonium nitrate.
 9. A composition according to claim 1 wherein said aminoalkanol material is present as a salt with a watersoluble carboxylic acid.
 10. A composition according to claim 1 wherein substantially all of said aminoalkanol material is on the surface of said particles.
 11. A composition according to claim 1 wherein the ##STR12## units are located substantially terminally on the ##STR13## chain.
 12. A composition according to claim 1 wherein y is O and R₃ and R₄ represent H.
 13. A composition according to claim 1 wherein y is O, R₃ is H and R₄ is --CH₃.
 14. A composition according to claim 1 wherein y is O, R₃ and R₄ are --CH₂ CH₂ OH.
 15. A composition according to claim 1 wherein y is 1, x is 2 and R₃ and R₄ are H.
 16. A composition according to claim 1 wherein x is 2, y is 1, R₃ is H and R₄ is --CH₂ CH₂ OH. 